Viscous materials, such as toothpaste, are commonly packaged in collapsible tubes which offer the advantages of low cost and ease of use. However, consumer satisfaction with tubes has been limited by their messiness and their appearance during storage and use. In addition, they can be inconvenient to store because they occupy a large area when laid flat.
More recently, mechanical pumps have been introduced with some success because they overcome the negative of poor appearance during use and provide ease of storage. However, their acceptance has been somewhat limited by poor economy and the difficulty they present in dispensing product. As a result, considerable interest has been shown in the use of resilient squeeze bottle packages for dispensing viscous products.
One such resilient squeeze bottle package which has been well received is disclosed in commonly assigned U.S. Pat. No. 4,842,165 issued to Van Coney on Jun. 27, 1989. The commonly assigned Van Coney patent discloses a resilient squeeze bottle dispensing package capable of dispensing viscous products without excessive air entrainment and belching on successive dispensing cycles. In a preferred embodiment, the viscous product is suspended inside a resilient squeeze bottle in a thin flexible bag. The flexible bag is secured about its perimeter to the interior of the squeeze bottle at its top and approximately at its midpoint to facilitate both complete emptying of product and desirable suckback characteristics when the opposed squeezing forces are removed from the resilient outer wall of the bottle. A suckback valve is preferably located between the dispensing orifice in the shroud of the package and the flexible bag to limit the amount of air which can enter the package through the dispensing orifice at the conclusion of each dispensing cycle and to prevent slumping of viscous product remaining in the shroud into the bottom of the flexible bag between dispensing cycles. An air check valve is preferably provided in the bottom of the resilient squeeze bottle to facilitate a pressure buildup within the bottle when opposed squeezing forces are applied to the bottle.
While the resilient squeeze bottle package disclosed by Van Coney has been found to function extremely well, an unexpected problem has been encountered with certain embodiments of the Van Coney package when the atmospheric pressure surrounding the package decreases. This would normally be the case when a package manufactured substantially at sea level is taken along during air travel to an elevation over 5000 feet above sea level or, for example, when the user transports the package via ground travel from a first elevation where the package has become equilibrated to the surrounding atmosphere to a substantially higher elevation in a relatively short period of time, e.g., as would be the case in driving from Denver, Colorado (elevation approximately 5,000 feet above sea level) to Aspen, Colorado (elevation approximately 8,000 feet above sea level).
Because the air check valve used in a particularly preferred embodiment of the Van Coney package traps air in the variable volume chamber formed between the bottom of the flexible bag and the inside of the resilient squeeze bottle when the surrounding atmospheric pressure decreases, the pressure differential acting upon the flexible bag may become sufficient to cause the viscous product to ooze from the dispensing orifice in the squeeze bottle in the event the closure is not tightly secured thereto. Furthermore, even if the closure is tightly secured during travel, the pressure differential which will exist at the time the closure is ultimately removed will cause uncontrollable oozing of viscous product from the dispensing orifice of the squeeze bottle until such time as the air pressure in the variable volume chamber of the package reaches equilibrium with that of the surrounding atmosphere.